The present invention relates to a locking device usable for mounting a sheet-shaped target member (e.g., an undercover) to a support member (e.g., a panel of an automotive vehicle) having a stud (e.g., a threaded stud) fixed thereto. More specifically, it relates to a stud locking device usable for mounting the target member to the support member, in such a manner that it is lockedly engaged with the stud while retaining the target member.
Generally, a locking device is employed as a means to mount a sheet-shaped target member such as an undercover to a support member such as a panel of an automotive vehicle. In advance of an operation of mounting a wide sheet-shaped target member such as an undercover to a panel, a plurality of threaded studs are fixedly attached onto the panel at respective given positions thereof by welding or the like, and a plurality of mounting holes for receiving therein the respective studs are formed in the undercover at respective given positions thereof. Then, the target member is put to the panel and positioned to allow the studs to be inserted into corresponding ones of the mounting holes of the target member, and a plurality of nuts are engaged, respectively, with portions of the studs protruding from the target member by using a tool. In this manner, the target member is mounted to a support member such as a panel of an automotive vehicle.
There has been known a stud locking device designed to facilitate such a target member mounting operation and configured to clamp a target member from both sides thereof by a first clip and a second clip, and, in this state, receive a stud into a stud-receiving hole of the locking device to thereby mount the target member to the stud.
Published Japanese application JP2007/292146 A and its US counterpart application US2007/0248436 A discloses this type of locking device (stud locking device) comprising a first clip and a second clip. The first clip comprises an inner cylindrical portion, a flange configured to come into contact with one of opposite surfaces of the target member, and locking pawls formed inside the inner cylindrical portion, and the second clip comprises an outer cylindrical portion; and a flange configured to come into contact with the other surface of the target member. The locking device disclosed in US2007/0248436 A is configured to be lockedly engaged with each of a plurality of studs fixedly attached to a support member such as a panel of an automotive vehicle, while clamping a sheet-shaped target member by the first clip and the second clip, thereby mounting the target member to the support member.
FIG. 1 illustrates the locking device 1′ disclosed in US2007/0248436 A. The locking device 1′ comprises a first clip 2 made of a hard synthetic resin (and molded as a single piece), and a second clip 3 made of a hard synthetic resin and molded as a single piece. The first clip 2 has an inner cylindrical portion 2b, and a flange 2a formed at one end of the inner cylindrical portion 2b. The second clip 3 has an outer cylindrical portion 3b, and a flange 3a formed at one end of the outer cylindrical portion 3b. The inner cylindrical portion 2b of the first clip 2 is inserted into a mounting hole 9 of a sheet-shaped target member 5 to be mounted, and further inserted into the outer cylindrical portion 3b of the second clip 3. Thus, the first clip 2 and the second clip 3 are couple together while clamping the target member 5 therebetween. When a stud 7 fixedly attached onto a support member 6 such as a panel of an automotive vehicle is inserted into a stud-receiving hole of the locking device 1′, a locking pawl 4 of the first clip 2 is lockedly engaged with a thread ridge of the stud 7, so that the target member 5 is mounted to the support member 6. A hexagonal hole 8 is formed in a central region of the flange of the first clip 2. Thus, a hexagonal wrench can be engaged with the hexagonal hole 8 and rotated to further tighten up or detach the locking device 1′ with respect to the stud 7.
In the locking device disclosed in US2007/0248436 A, the hexagonal hole is formed in a central portion of the first clip 2 to allow the hexagonal wrench to be rotated while being inserted therein. The hexagonal hole has a relatively small diameter and a relatively long length so as to ensure engagement with the hexagonal wrench, and thus it is difficult to visually ascertain how much the first clip is inserted with respect to the stud, even when viewed from above the hexagonal hole. If the first clip is not fully inserted, a pull-out load is likely to decrease. Moreover, in the locking device disclosed in US2007/0248436 A, a bottom of the first clip does not have a taper wall for allowing the stud to be received in the stud-receiving hole. Thus, when the stud is inserted into the stud-receiving hole, it is likely that there is difficulty in guiding and inserting the stud with respect to the stud-receiving hole.
Published Japanese application JP2009/162358 A discloses a stud bolt clip lockable to a stud bolt provided to stand on a vehicle panel of an automotive vehicle, or the like. The stud bolt clip is a single component. The stud bolt clip comprises: a pair of first locking members each formed to extend from a corner of a bolt insertion hole-side end of an inner surface of a respective one of two opposed sidewall portions, in such a manner that they are disposed in opposed relation to each other; and a pair of second locking members each formed to extend from an axially approximately central region of the inner surface of the respective one of the opposed sidewall portions, in such a manner that they are disposed in opposed relation to each other. Each of the first locking members has an inner surface formed with three first locking ribs engageable with thread grooves of a first stud bolt having a relatively small thread pitch, and each of the second locking members has an inner surface formed with three second locking ribs engageable with thread grooves of a second stud bolt having a relatively large thread pitch.
In an operation for locking to the first stud bolt having a relatively small thread pitch, the three first locking ribs are engaged with thread grooves of the first stud bolt, and either one of the three second locking ribs is engaged with a thread groove of the first stud bolt. In an operation for locking to the second stud bolt having a relatively large thread pitch, either one of the three first locking ribs is engaged with a thread groove of the second stud bolt, and the three second locking ribs are engaged with thread grooves of the second stud bolt.
The stud bolt clip disclosed in JP2009/162358 A can be locked to each of two types of stud bolts having different pitches. However, when the stud bolt clip is locked to the first stud bolt, only a part of the three second locking ribs is engaged with a thread groove of the second stud bolt. On the other hand, when the stud bolt clip is locked to the second stud bolt, only a part of the three first locking ribs is engaged with a thread groove of the first stud bolt. Thus, the stud bolt clip is likely to fail to be reliable mounted. Further, in an operation of attaching the stud bolt clip to a target member to be mounted, a pair of clamping ribs are inserted, respectively, into a pair of member through-grooves, and turned 90° to clamp the target member between the clamping ribs and a flange of the stud bolt clip. Thus, it is necessary to form, in the target member, a mounting hole together with the pair of quadrangular-shaped member through-grooves, i.e., take a lot of time and effort for processing of the target member.
Therefore, there is a need for a stud locking device capable of mounting a target member such as an undercover to a support member such as a panel of an automotive vehicle, readily and reliably. There is also a need for a stud locking device capable of readily ascertaining whether a clip is perfectly mounted to a stud.